<template>
    <div class="s-canvas">
        <canvas id="s-canvas" :width="contentWidth" :height="contentHeight"></canvas>
    </div>
</template>

<script>

export default {
    name:'SIdentify',
    props:{
        identifyCode:{
            type: String,
            default: '1234',
        },
        fontSizeMin:{
            type: Number,
            default: 25,
        },
        fontSizeMax:{
            type: Number,
            default: 30,
        },
        backgroundColorMin:{
            type: Number,
            default: 255,
        },
        backgroundColorMax:{
            type: Number,
            default: 255,
        },
        colorMin:{
            type: Number,
            default: 0,
        },
        colorMax:{
            type: Number,
            default: 160,
        },
        lineColorMin:{
            type: Number,
            default: 100,
        },
        lineColorMax:{
            type: Number,
            default: 255,
        },
        dotColorMin:{
            type: Number,
            default: 0,
        },
        dotColorMax:{
            type: Number,
            default: 255,
        },
        contentWidth:{
            type: Number,
            default: 132,
        },
        contentHeight:{
            type: Number,
            default: 31,
        }
    },
    methods:{
        // 生成一个随机数
        randomNum(min, max) {
            return Math.floor (Math.random() * (max - min) + min)
        },
        //生成一个随机的颜色
        randomColor(min, max) {
            let r = this. randomNum(min,max )
            let g = this. randomNum(min, max)
            let b = this.randomNum(min, max)
            return' rgb( ' + r +','+ g + ',' + b +')'
        },
        drawPic() {
            let canvas = document.getElementById('s-draw')
            let ctx = canvas.getContext('2d')
            ctx.textBaseline = 'bottom'
            //绘制背景
            ctx.fillstyle = this.randomColor(
                this.backgroundcolorMin,
                this.backgroundColorMax
            )
            ctx.fillRect(0, 0, this.contentwidth, this.contentHeight)
            //绘制文字
            for (let i = 0; i < this.identifyCode.length; i++) {
                this.drawText(ctx, this.identifyCode[i], i)
            }
                this.drawLine(ctx) 
                this.drawDot(ctx)
        },
        drawText(ctx, txt, i) {
            ctx.fillstyle = this.randomcolor(this.colorMin, this.colorMax)
            ctx.font =
                this.randomNum(this.fontSizeMin, this.fontSizeMax) + 'px SimHei'
            let x = (i+1) * (this.contentwidth / (this.identifyCode.length + 1))
            let y = this.randomNum(this.fontSizeMax, this.contentHeight - 5)
            var deg = this.randomNum(-45, 45)
            //修改坐标原点和旋转角度
            ctx.translate(x, y)
            ctx.rotate((deg * Math.PI) / 180)
            ctx.fillText(txt, 0, 0)
            //恢复坐标原点和旋转角度
            ctx.rotate((-deg * Math.PI) / 180)
            ctx.translate(-x, -y)
        },
        drawLine(ctx) {
            // 绘制干扰线
            for (let i = 0; i < 5; i++) {
                ctx.strokeStyle = this.randomColor(this.lineColorMin, this.lineColorMax)
                ctx.beginPath()
                ctx.moveTo(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight))
                ctx.lineTo(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight))
                ctx.stroke()
            }
        },
        drawDot(ctx) {
            // 绘制干扰点
            for (let i = 0; i < 80; i++) {
                ctx.fillStyle = this.randomColor(0, 255)
                ctx.beginPath()
                ctx.arc(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight), 1, 0, 2 * Math.PI)
                ctx.fill()
            }
        }
    },
    watch:{
        identifyCode(){
            this.drawPic()
        }
    },
    mounted(){
        this.drawPic()
    }
}
</script>

<style scoped>
.s-canvas{
    height: 38px;
}
.s-canvas canvas{
    margin-top: 5px;
    margin-left: 8px;
}
</style>
